Best way to stuff capacitor ?

[tim.54]

Have removed the chassis from the marconi 556 , about to swop the capacitors , each capacitor has its own metal recess in which it sits acting as a support for other attached components , so will need to restuff them .The 0.1 uf ones are quite large 2.5inch by 1 inch ! looks to be a tar like substance in each end , best way to remove and what to refill with , all advice welcomed , regards, tim.